1. Field of the Invention
The present invention relates to an electrophotographic photosensitive member, and a process cartridge and an electrophotographic apparatus having an electrophotographic photosensitive member.
2. Description of the Related Art
As electrophotographic photosensitive members used for process cartridges and electrophotographic apparatuses, electrophotographic photosensitive members containing an organic photoconductive substance mainly prevail at present. The electrophotographic photosensitive member generally has a support and a photosensitive layer formed on the support. Then, an undercoating layer is provided between the support and the photosensitive layer in order to suppress the charge injection from the support side to the photosensitive layer (charge generating layer) side and to suppress the generation of image defects such as fogging.
Charge generating substances having a higher sensitivity have recently been used. However, such a problem arises that a charge is liable to be retained in a photosensitive layer due to that the amount of charge generated becomes large along with making higher the sensitivity of the charge generating substance, and the ghost is liable to occur. Specifically, a phenomenon of a so-called positive ghost, in which the density of only portions irradiated with light in the preceding rotation time becomes high, is liable to occur in a printed-out image.
A technology of reducing such a ghost phenomenon is disclosed in which an undercoating layer is made to be a layer (hereinafter, also referred to as an electron transporting layer) having an electron transporting capability by incorporating an electron transporting substance in the undercoating layer. National Publication of International Patent Application No. 2009-505156 discloses a condensed polymer (electron transporting substance) having an aromatic tetracarbonylbisimide skeleton and a crosslinking site, and an electron transporting layer containing a polymer with a crosslinking agent. Japanese Patent Application Laid-Open No. 2003-330209 discloses that a polymer of an electron transporting substance having a non-hydrolyzable polymerizable functional group is incorporated in an undercoating layer. Japanese Patent Application Laid-Open No. 2005-189764 discloses a technology of making the electron mobility of an undercoating layer to be 10−7 cm2/V·sec or more in order to improve the electron transporting capability.
The demand for the quality of electrophotographic images has recently been raised increasingly, and the allowable range for the early-stage positive ghost and the long-term positive ghost after repeated use has remarkably become severe. As a result of exhaustive studies by the present inventors, it has been found that with respect to the reduction of the positive ghost, technologies disclosed in National Publication of International Patent Application No. 2009-505156 and Japanese Patent Application Laid-Open Nos. 2003-330209 and 2005-189764 still have room for improvement.